From the past, a member capable of transmitting millimeter electromagnetic waves and the like while having a metallic appearance has been contrived as a casing component of electronic apparatuses and the like. For example, Patent Literature 1 discloses an exterior component for mounting an automotive radar on an automotive emblem. For example, indium is vapor-deposited on a resin film, and this film is attached to a surface layer of the emblem by an insert molding method. As a result, it becomes possible to produce an exterior component that has metallic luster and does not have an absorption range in an electromagnetic wave frequency band due to an island-like configuration of indium (paragraph [0006] in specification of Patent Literature 1 etc.).
Patent Literature 1 also discloses the following technology. Specifically, a sea-island configuration in which metal regions are islands and a nonmetal region surrounding the islands is the sea is formed artificially while having regularity. In addition, the metal regions are insulated from one another by the nonmetal region, and areas of the metal regions and distances among the adjacent metal regions are controlled appropriately. There is a description that a material having electromagnetic wave permeability that compares well with a film onto which indium is vapor-deposited can consequently be obtained (paragraph [0013] in specification of Patent Literature 1 etc.).